As every motorist knows, sun visors are placed in automobiles to shield the sun from the driver's eyes whenever he is driving into the sun, and also when the sun is to the left of him. Because the driver must see where he is going, the position of the lower edge of the sun visor is predetermined. However, when the sun is at a low angle, the sun visor is not effective. This condition is not as dangerous as when he is ascending a hill, because now the actual earth azimuth angle of the sun is relatively large and its rays are bright, but the angle the sun makes with respect to the vehicle is much smaller to allow the bright rays to shine into the driver's eyes, as the sun visor inherently cannot shield them.
In the past, various means have been employed to further block out sun rays from the driver's eyes. For example, U.S. Pat. No. 3,853,370 teaches a means for holding a transparent glare shield onto the sun visor, which allows one to pull down the glare shield against the action of the spring. U.S. Pat. No. 3,837,703 teaches a means which allows one to rotate a glare shield downward. Although these prior art devices help to alleviate the dangerous effects of the sun rays, they are complicated and have limited utility.